Sinclair International has created a series of helpful articles on rifle cartridge reloading. Today’s feature lists ten basic steps for precision hand-loading, with links to longer, detailed Sinclair Int’l technical articles providing more complete information. There’s a lot of helpful info here guys, if you click all the links to access the ten “long form” articles.
Tying It All Together: 10 Steps To Precision Handloads
Feature based on article by Roy Hill, Brownells/Sinclair Copywriter
Sinclair International offers a series of detailed articles on hand-loading precision rifle ammunition. The articles are included in Sinclair’s GunTech Articles Archive, but sorting through the index to find each article takes time. To help you access all these articles quickly, here’s a handy summary of ten key topics, with links to longer articles covering each subject in detail.
Part 1: The first step in making high-quality handloads is to carefully choose the best brass for your application. You need to know how to identify the different types of brass and how to choose the best kind for the ammo you want to load. CLICK HERE for Part 1.
Part 2: Even high-quality brass can have burrs around the flash hole that can interfere with the primer flame and cause inconsistent ignition – which can lead to shot groups opening up. Flash hole deburring is a critical step in making sure primers ignite powder consistently. CLICK HERE for Part 2.
Part 3: The next step is to make sure the primer pockets are square and uniform. Like flash hole deburring, primer pocket uniforming may reduce variations in primer ignition by ensuring more consistent primer seating. CLICK HERE for Part 3.
Part 4: Making sure all your cases are precisely the same length is crucial, especially when you use cases that have been fired before. Case trimming is the way to get there. CLICK HERE for Part 4.
Part 5: After trimming, cases still have to be resized. In order for them to work through the resizing die, they have to be lubricated. The case lube method you choose is crucial to making precision handloads. CLICK HERE for Part 5.
Part 6: Now it’s time to choose the dies that will resize your cases. There are several important options to consider in selecting the right sizing dies. CLICK HERE for Part 6.
Part 7: Wait! You’re not quite ready to start sizing yet. There’s yet more to consider before you start cranking cases through the press. Learn more about setting up and adjusting your sizing dies. CLICK HERE for Part 7.
Part 8: Once the cases are completely prepped, it’s time to start putting fresh components back into them. We start off by seating primers. CLICK HERE for Part 8.
Part 9: After the primers are seated, it’s time to drop in the powder. There are several tools that will help you handle powder for precision handloads. CLICK HERE for Part 9.
Part 10: The final step in the process is carefully seating the bullet to just the right depth. And then… you’re ready to try your loads at the range. CLICK HERE for Part 10.
Share the post "Precision Handloading — TEN Important Steps — Start to Finish"
Figure 1. When the bullet is seated farther out of the case, there is more volume available for powder. This enables the cartridge to generate higher muzzle velocity with the same pressure.
Effects Of Cartridge Over All Length (COAL) And Cartridge Base To Ogive (CBTO) – Part 1 by Bryan Litz forBerger Bullets.
Many shooters are not aware of the dramatic effects that bullet seating depth can have on the pressure and velocity generated by a rifle cartridge. Cartridge Overall Length (COAL) is also a variable that can be used to fine-tune accuracy. It’s also an important consideration for rifles that need to feed rounds through a magazine. In this article, we’ll explore the various effects of COAL, and what choices a shooter can make to maximize the effectiveness of their hand loads.
Sporting Arms and Ammunition Manufacturers’ Institute (SAAMI)
Most loading manuals (including the Berger Manual), present loading data according to SAAMI (Sporting Arms and Ammunition Manufacturers’ Institute) standards. SAAMI provides max pressure, COAL and many other specifications for commercial cartridges so that rifle makers, ammo makers, and hand loaders can standardize their products so they all work together. As we’ll see later in this article, these SAAMI standards are in many cases outdated and can dramatically restrict the performance potential of a cartridge.
Bullet seating depth is an important variable in the accuracy equation. In many cases, the SAAMI-specified COAL is shorter than what a hand loader wants to load their rounds to for accuracy purposes. In the case where a hand loader seats the bullets longer than SAAMI specified COAL, there are some internal ballistic effects that take place which are important to understand.
Effects of Seating Depth / COAL on Pressure and Velocity
The primary effect of loading a cartridge long is that it leaves more internal volume inside the cartridge. This extra internal volume has a well known effect; for a given powder charge, there will be less pressure and less velocity produced because of the extra empty space. Another way to look at this is you have to use more powder to achieve the same pressure and velocity when the bullet is seated out long. In fact, the extra powder you can add to a cartridge with the bullet seated long will allow you to achieve greater velocity at the same pressure than a cartridge with a bullet seated short.
When you think about it, it makes good sense. After all, when you seat the bullet out longer and leave more internal case volume for powder, you’re effectively making the cartridge into a bigger cartridge by increasing the size of the combustion chamber. Figure 1 illustrates the extra volume that’s available for powder when the bullet is seated out long.
Before concluding that it’s a good idea to start seating your bullets longer than SAAMI spec length, there are a few things to consider.
Geometry of a Chamber Throat
The chamber in a rifle will have a certain throat length which will dictate how long a bullet can be loaded. The throat is the forward portion of the chamber that has no rifling. The portion of the bullet’s bearing surface that projects out of the case occupies the throat (see Figure 2).
The length of the throat determines how much of the bullet can stick out of the case. When a cartridge is chambered and the bullet encounters the beginning of the rifling, known as the lands, it’s met with hard resistance. This COAL marks the maximum length that a bullet can be seated. When a bullet is seated out to contact the lands, its initial forward motion during ignition is immediately resisted by an engraving force.
Seating a bullet against the lands causes pressures to be elevated noticeably higher than if the bullet were seated just a few thousandths of an inch off the lands.
A very common practice in precision reloading is to establish the COAL for a bullet that’s seated to touch the lands. This is a reference length that the hand loader works from when searching for the optimal seating depth for precision. Many times, the best seating depth is with the bullet touching or very near the lands. However, in some rifles, the best seating depth might be 0.100″ or more off the lands. This is simply a variable the hand loader uses to tune the precision of a rifle.
Every year at SHOT Show in January, bullet-makers showcase their latest and greatest projectiles for hunters and paper-punchers. we plan to get the “inside scoop” on new bullet designs from Berger, Hornady, Lapua, Nosler and Sierra.
A while back, at SHOT Show 2012 we chatted with Berger Ballistician Bryan Litz about Berger’s popular line of Hybrid bullets. Berger now offers a wide range of Hybrids in multiple calibers and weights. In fact, for .30-Caliber shooters, Berger now offers many seven (7) Hybrid match bullets, with weights from 155 grains up to 230 grains. Two .338-caliber OTM Tactical Hybrids were introduced in 2012 (a 250-grainer and a 300-grainer).
Bryan tells us: “The hybrid design is Berger’s solution to the age old problem of precision vs. ease of use. This design is making life easier for handloaders as well as providing opportunities for commercial ammo loaders who need to offer a high performance round that also shoots precisely in many rifles with various chamber/throat configurations.”
For those not familiar with Hybrid bullets, the Hybrid design blends two common bullet nose shapes on the front section of the bullet (from the tip to the start of the bearing surface). Most of the curved section of the bullet has a Secant (VLD-style) ogive for low drag. This then blends in a Tangent-style ogive curve further back, where the bullet first contacts the rifling. The Tangent section makes seating depth less critical to accuracy, so the Hybrid bullet can shoot well through a range of seating depths, even though it has a very high Ballistic Coefficient (BC).
In the video we asked Bryan for recommended seating depths for 7mm and .30-Caliber Hybrid bullets. Bryan advises that, as a starting point, Hybrid bullets be seated .015″ (fifteen thousandths) off the lands in most barrels. Watch the video for more tips how to optimize your loads with Hybrid bullets.
Share the post "Hybrid Bullets: How to Optimize Your Seating Depths"
Here’s a helpful hint for hand-loaders from Sierra Bullets. While this article focuses on Sierra’s new Tipped Match-King bullets, the recommended solutions apply to other bullet types as well. The article explains how sharp edges on a seating stem can cause a ring to be pressed into the bullet jacket — especially with compressed loads that resist downward bullet movement. Here Sierra technician Rich Machholz diagnoses the problem and provides a solution.
Solutions for Ring Marks Caused by Seating Stems
by Sierra Bullets Ballistic Technician Rich Machholz
Now that the new Tipped MatchKing® (TMK) bullets are being shipped and shooters are putting them to use I have received several calls regarding marking on the bullet ogive from the seating stem.
The cause can be traced to one of several things. In the .223 and especially with the long, 77 grain TMK seated at 2.250” or even 2.260” most loads of Varget® and Reloder® 15 are compressed loads, sometimes heavily compressed. This puts a great deal of pressure on the bullet through the seating stem. The result of all this pressure is a mark of varying depth and appearance on the ogive of the bullet. [Editor: We have seen this issue with a variety of other bullet types/shapes as well, including non-tipped VLDs. The solution is profiling the internal cone of the seating stem to match your bullet shape.]
Some older seating stems might even bear against the tip of the bullet which can make a slight bulge in the jacket just below the junction of the resin tip and the copper jacket in a compressed load. If this is the case there is not a ready fix other than calling the die manufacturer and requesting a new deeper seating stem.
Polish Your Seating Stem to Remove Sharp Internal Edges
If the seating stem is of proper depth the culprit most generally is a thin sharp edge on the inside taper of the seating stem. This is an easy fix that can be accomplished by chucking a spare 77 grain bullet in your drill, coating it with valve grinding compound or even rubbing compound or in a pinch even tooth paste.* Remove the seating stem assembly from the seating die. Turn the drill on and put the seating stem recess over the spinning bullet with the polishing compound to break or smooth the sharp edge that is making the offending mark. This might take more than one application to get the proper polish depending upon what you use, but the more you polish the better the blend of angles which will [ensure the stem matches the bullet contours, not leaving a sharp ring].
If the above is a little more than you care to tackle you might try very fine emery cloth twisted to a point that can be inserted into the mouth to the seating stem and rotated to polish the inside to eliminate any sharp edges that might be present.
Load Advice for 77gr TMKs in the .223 Rem
And last but certainly not least. Actually, even though we don’t say you need additional data for the TMKs, remember you are dealing with heavily-compressed loads in some cases because of the additional bullet length. Due to the additional length of these new bullets and in the interest of gaining some room in the case you might consider trying a slightly faster extruded powder like BenchMark or the 4895s or an even more dense powder like the spherical H335®, CFE223 or TAC. The extra room will allow for trouble free bullet seating also.
Good luck and remember we are no further away than your telephone: 1-800-223-8799.
Share the post "TIP: Polish Seating Stems to Eliminate Ring Marks on Bullets"
Here is a simple technique that can potentially help you load straighter ammo, with less run-out (as measured on the bullet). This procedure costs nothing and adds only a few seconds to the time needed to load a cartridge. Next time you’re loading ammo with a threaded (screw-in) seating die, try seating the bullet in two stages. Run the cartridge up in the seating die just enough to seat the bullet half way. Then lower the cartridge and rotate it 180° in the shell-holder. Now raise the cartridge up into the die again and finish seating the bullet.
Steve, aka “Short Range”, one of our Forum members, recently inquired about run-out apparently caused by his bullet-seating process. Steve’s 30BR cases were coming out of his neck-sizer with good concentricity, but the run-out nearly doubled after he seated the bullets. At the suggestion of other Forum members, Steve tried the process of rotating his cartridge while seating his bullet. Steve then measured run-out on his loaded rounds. To his surprise there was a noticeable reduction in run-out on the cases which had been rotated during seating. Steve explains: “For the rounds that I loaded yesterday, I seated the bullet half-way, and turned the round 180 degrees, and finished seating the bullet. That reduced the bullet runout by almost half on most rounds compared to the measurements from the first test.”
Steve recorded run-out measurements on his 30BR brass using both the conventional (one-pass) seating procedure, as well as the two-stage (with 180° rotation) method. Steve’s measurements are collected in the two charts above. As you can see, the run-out was less for the rounds which were rotated during seating. Note, the change is pretty small (less than .001″ on average), but every little bit helps in the accuracy game. If you use a threaded (screw-in) seating die, you might try this two-stage bullet-seating method. Rotating your case in the middle of the seating process won’t cost you a penny, and it just might produce straighter ammo (nothing is guaranteed). If you do NOT see any improvement on the target, you can always go back to seating your bullets in one pass. READ Forum Thread..
Share the post "Try Rotating Cases During Bullet Seating to Reduce Run-Out"
Sinclair International has created a series of helpful articles on rifle cartridge reloading. Today’s feature lists ten basic steps for precision hand-loading, with links to longer, detailed Sinclair Int’l technical articles providing more complete information. There’s a lot of helpful info here guys, if you click all the links to access the ten “long form” articles.
Tying It All Together: 10 Steps To Precision Handloads
Feature based on article by Roy Hill, Brownells/Sinclair Copywriter
Sinclair International offers a series of detailed articles on hand-loading precision rifle ammunition. The articles are included in Sinclair’s GunTech Articles Archive, but sorting through the index to find each article takes time. To help you access all these articles quickly, here’s a handy summary of ten key topics, with links to longer articles covering each subject in detail.
Part 1: The first step in making high-quality handloads is to carefully choose the best brass for your application. You need to know how to identify the different types of brass and how to choose the best kind for the ammo you want to load. CLICK HERE for Part 1.
Part 2: Even high-quality brass can have burrs around the flash hole that can interfere with the primer flame and cause inconsistent ignition – which can lead to shot groups opening up. Flash hole deburring is a critical step in making sure primers ignite powder consistently. CLICK HERE for Part 2.
Part 3: The next step is to make sure the primer pockets are square and uniform. Like flash hole deburring, primer pocket uniforming may reduce variations in primer ignition by ensuring more consistent primer seating. CLICK HERE for Part 3.
Part 4: Making sure all your cases are precisely the same length is crucial, especially when you use cases that have been fired before. Case trimming is the way to get there. CLICK HERE for Part 4.
Part 5: After trimming, cases still have to be resized. In order for them to work through the resizing die, they have to be lubricated. The case lube method you choose is crucial to making precision handloads. CLICK HERE for Part 5.
Part 6: Now it’s time to choose the dies that will resize your cases. There are several important options to consider in selecting the right sizing dies. CLICK HERE for Part 6.
Part 7: Wait! You’re not quite ready to start sizing yet. There’s yet more to consider before you start cranking cases through the press. Learn more about setting up and adjusting your sizing dies. CLICK HERE for Part 7.
Part 8: Once the cases are completely prepped, it’s time to start putting fresh components back into them. We start off by seating primers. CLICK HERE for Part 8.
Part 9: After the primers are seated, it’s time to drop in the powder. There are several tools that will help you handle powder for precision handloads. CLICK HERE for Part 9.
Part 10: The final step in the process is carefully seating the bullet to just the right depth. And then… you’re ready to try your loads at the range. CLICK HERE for Part 10.
Share the post "Precision Hand-Loading — Ten Steps Explained by Sinclair Int’l"
Here’s a tip we feature every year or so, because it is something that costs nothing, yet can be very useful in the reloading process. With a simple, easy modification to a fired case, you can determine the length to lands in your rifle barrel. As long as you set the tension right, the measurements should be repeatable, and you’ve just saved yourself $31 — the price of a commercial OAL gauge.
To achieve best accuracy with a rifle, you must control bullet seating depth very precisely, so all bullets end up in the same place relative to the entrance of the lands, every time. There may be multiple cartridge OALs which prove accurate. However, with each, you first need to determine a “zero” point — a reliable, and repeatable OAL where the bullet is “just touching” the lands.
There are tools, such as the Hornady (formerly Stoney Point) OAL Gauge, that will help you find a seating OAL just touching the lands. However, the tool requires that you use a special modified case for each cartridge you shoot. And, while we find that the Hornady OAL Gauge is repeatable, it does take some practice to get in right.
Make Your Own Length-to-Lands Gauge with a Dremel
Here’s an inexpensive alternative to the Hornady OAL tool — a slotted case. Forum member Andris Silins explains how to create a slotted case to measure length to the lands in your rifle:
“Here’s what I did to find length to lands for seating my bullets. I made four cuts into the neck of fire-formed brass. Then I pressed the bullet in lightly and chambered the entire gauge. As the cartridge chambers, the bullet slides back into the case to give you length to lands. It took less than five minutes to get it cut and working. A little light oil in the barrel just past the chamber helps ensure the bullet does not get stuck in the lands. It works great and is very accurate.
I made the cuts using a Dremel with a cut-off wheel. You can adjust tension two ways. First, you can make the cuts longer or shorter. Longer cuts = less tension. If you used only three cuts insted of four you would get more tension. The trick is to be gentle when you open and close the bolt. If you ram the bolt closed you may wedge the bullet into the lands. When you open the bolt it helps to keep a finger or two near by to guide the case out straight because the ejector wants to push it sideways.”
Share the post "Smart Tool Tip: Make Your Own Length-to-Lands Gauge"
Here’s a helpful hint for hand-loaders from Sierra Bullets. While this article focuses on Sierra’s new Tipped Match-King bullets, the recommended solutions apply to other bullet types as well. The article explains how sharp edges on a seating stem can cause a ring to be pressed into the bullet jacket — especially with compressed loads that resist downward bullet movement. Here Sierra technician Rich Machholz diagnoses the problem and provides a solution.
Solutions for Ring Marks Caused by Seating Stems
by Sierra Bullets Ballistic Technician Rich Machholz
Now that the new Tipped MatchKing® (TMK) bullets are being shipped and shooters are putting them to use I have received several calls regarding marking on the bullet ogive from the seating stem.
The cause can be traced to one of several things.
In the .223 and especially with the long, 77 grain TMK seated at 2.250” or even 2.260” most loads of Varget® and Reloder® 15 are compressed loads, sometimes heavily compressed. This puts a great deal of pressure on the bullet through the seating stem. The result of all this pressure is a mark of varying depth and appearance on the ogive of the bullet. [Editor: We have seen this issue with a variety of other bullet types/shapes as well, including non-tipped VLDs. The solution is profiling the internal cone of the seating stem to match your bullet shape.]
Some older seating stems might even bear against the tip of the bullet which can make a slight bulge in the jacket just below the junction of the resin tip and the copper jacket in a compressed load. If this is the case there is not a ready fix other than calling the die manufacturer and requesting a new deeper seating stem.
Polish Your Seating Stem to Remove Sharp Internal Edges
If the seating stem is of proper depth the culprit most generally is a thin sharp edge on the inside taper of the seating stem. This is an easy fix that can be accomplished by chucking a spare 77 grain bullet in your drill, coating it with valve grinding compound or even rubbing compound or in a pinch even tooth paste.* Remove the seating stem assembly from the seating die. Turn the drill on and put the seating stem recess over the spinning bullet with the polishing compound to break or smooth the sharp edge that is making the offending mark. This might take more than one application to get the proper polish depending upon what you use, but the more you polish the better the blend of angles which will [ensure the stem matches the bullet contours, not leaving a sharp ring].
If the above is a little more than you care to tackle you might try very fine emery cloth twisted to a point that can be inserted into the mouth to the seating stem and rotated to polish the inside to eliminate any sharp edges that might be present.
Load Advice for 77gr TMKs in the .223 Rem
And last but certainly not least. Actually, even though we don’t say you need additional data for the TMKs, remember you are dealing with heavily-compressed loads in some cases because of the additional bullet length. Due to the additional length of these new bullets and in the interest of gaining some room in the case you might consider trying a slightly faster extruded powder like BenchMark or the 4895s or an even more dense powder like the spherical H335®, CFE223 or TAC. The extra room will allow for trouble free bullet seating also.
Good luck and remember we are no further away than your telephone: 1-800-223-8799.
Share the post "Bullet Seating Advice — How to Avoid Ring Marks on Your Bullets"
In this video, Forum member Erik Cortina shows how to create a custom modified case for use with the Hornady Lock-N-Load Overall Length Gauge (formerly the Stoney Point Tool). While Hornady sells modified cases for many standard cartridges, if you shoot a wildcat such as the 6mm Dasher or .284 Shehane, you’ll need to create a custom modified case*. And even if you shoot a standard cartridge such as the .308 Winchester you can get more consistent measurements if you make a custom modified case from a piece of brass fired in your chamber.
The process is straight-forward. Take a piece of brass fired in your chamber and full-length size it (with about .002″ shoulder bump). Then you need to drill out the primer pocket. Erik uses a mini-lathe for the operation, but this general process can be done with a drill press or other tools. Erik shows how to do this with a 0.290″ HSS (High Speed Steel) drill bit on a mini-lathe. After drilling the hole comes the tricky part — you need to tap the case with the precise 5/16″ x 36 threads per inch (tpi) right-hand thread that matches the male thread on the O.A.L. Gauge. This 5/16″ x 36 tpi tap is pretty uncommon, but you can order it from Amazon.com if you can’t source it locally.
If you use a mini-lathe, Erik suggests loosening the tailstock slightly, so it can float while cutting the threads. Erik also says: “Make sure you get the tap on pretty tight — it’s going to want to spin.” Erik turns the case at about 100 rpm when tapping the threads. Once the case and tap are rigged, the actual tapping process (see video at 6:00) takes only a few seconds. While the mini-lathe makes the tapping process go more quickly, the threading can also be done with other systems.
TIP: Don’t just make one modified case, make three. That gives you one for your range kit, one for your home reloading bench, plus a spare (since you WILL eventually lose or misplace one).
Here’s the Stuff You Need
5/16″-36 TPI Threading Tap
The required thread is somewhat uncommon. You need a 5/16″ – 36 tpi Right Hand Thread Tap. If you can’t find it locally, Amazon.com carries the correct tap. Erik notes: “The 5/16-36 tpi tap is not a common size. I think Hornady did this on purpose to make it more difficult for the average guy to make his own modified cases.”
0.290″ Drill Bit
Erik uses an 0.290″ HSS “L” drill bit. (This “L” Letter Gauge code designates a 0.290″ diameter bit). A close metric equivalent would be 7.3 mm (0.286″). Erik says: “A 9/32″ drill will also work but it will be harder to run the tap in since the hole will be .281″ instead of .290″ with the Letter Gauge L bit.”
Tips for Using O.A.L. Gauge with Modified Case
We’ve noticed that many folks have trouble getting reliable, consistent results when they first start using the Hornady O.A.L. Gauge (formerly the Stoney Point Tool). We’ve found this is usually because they don’t seat the modified case properly and because they don’t use a gentle, consistent method of advancing the bullet until it just kisses the lands.
Here is our suggested procedure for use the O.A.L. Gauge. Following this method we can typically make three of four measurements (with the same bullet), all within .001″ to .0015″. (Yes, we always measure multiple times.)
1. Clean your chamber so there is no build-up of carbon, debris, or lube. Pay particular attention to the shoulder area.
2. Screw the modified case on to the O.A.L. Gauge. Make sure it is seated firmly (and doesn’t spin loose). Note, you may have to re-tighten the modified case after insertion in the chamber.
3. Place your selected bullet so that the ogive (max bullet diameter) is behind the case mouth. This prevents the bullet from “snagging” as you insert the tool in the action.
4. Insert the O.A.L. Gauge into your chamber smoothly. Push a little until you feel resistance. IMPORTANT — You need to ensure that the shoulder of the modified case is seated firmly against the front of your chamber. You may have to wiggle and twist the tool slightly. If you do not have the modified case seated all the way in, you will NOT get a valid measurement.
5. Advance the bullet slowly. (NOTE: This is the most important aspect for consistency!). Push the rod of the O.A.L. tool gently towards the chamber. DON’T shove it hard! Easy does it. Stop when you feel resistance.
6. IMPORTANT. After gently pushing on the rod, give the end of the rod a couple forward taps with your finger. If your bullet was slightly skewed, it may have stopped too far back. Adding a couple extra taps will fix that. If the bullet moves after the taps, then again push gently on the rod. NOT too much! You just want to push the bullet until it just “kisses” the lands and then stops. Do NOT jam the bullet into the rifling. If you do that you will never get consistent results from one measurement to the next.
* For a $15.00 fee, Hornady will make a custom modified case for you if you send two fired pieces of brass. Send fired cases and $15.00 check to: Hornady Manufacturing, Attn: Modified Cases, 108 S. Apollo St., Alda, NE 68810. More Info HERE.
Share the post "Make Your Own Modified Case for Hornady O.A.L. Gauge"
Effects Of Cartridge Over All Length (COAL) And Cartridge Base To Ogive (CBTO) – Part 2 by Bryan Litz forBerger Bullets. Part One of this series focused on the importance of COAL in terms of SAAMI standards, magazine lengths, seating depths, and pressure levels. Another measure of length for loaded ammunition is highly important to precision, namely Cartridge Base to Bullet Ogive Length (CBTO).
Figure 2. Chamber throat geometry showing the bullet jump to the rifling or lands.
Look at Figure 2. Suppose the bullet was seated out of the case to the point where the base of the bullet’s nose (ogive) just contacted the beginning of the riflings (the lands) when the bolt was closed. This bullet seating configuration is referred to as touching the lands, or touching the riflings and is a very important measurement to understand for precision hand-loading. Due to the complex dynamics of internal ballistics which happen in the blink of an eye, the distance a bullet moves out of the case before it engages the riflings is highly critical to precision potential. Therefore, in order to systematically optimize the precision of his handloads, it’s critically important that the precision hand-loader understands how to alter bullet seating depth in relation to the barrel rifling. Part of the required knowledge is understanding how to accurately and repeatably measure the Cartridge Base To Ogive (CBTO) dimension. This is explained in the FULL ARTICLE.
Bryan Litz offers an extended discussion on how to measure CBTO using different tools and methods, including the Hornady OAL gauge. You can read this discussion in the full article found on the Berger Bullets website. CLICK HERE to Read Full Article.
Why Not Use CBTO as a SAAMI Standard?
If CBTO is so important to rifle accuracy, you might ask, “Why is it not listed as the SAAMI spec standard in addition to COAL?” There is one primary reason why it is not listed in the standard. This is the lack of uniformity in bullet nose shapes and measuring devices used to determine CBTO.
Figure 4. Two different bullet shapes, seated to the same CBTO length, but different COAL. Note the shiny scratches on the bullets made by the comparator tool which indicates a point on the bullet ogive near where the ogive will engage the riflings.
Benefits of Having a Uniform CBTO
There is another aspect to knowing your CBTO when checking your COAL as it pertains to performance. With good bullets, tooling, and carefully-prepared cases you can easily achieve a CBTO that varies less than +/- .001″ but your COAL can vary as much as .025″ extreme spread (or more with other brands). This is not necessarily bad and it is much better than the other way around. If you have a CBTO dimension that varies but your COAL dimension is tight (within +/- .002″) then it is most likely that your bullet is bottoming out inside the seater cone on the bullet tip. This is very bad and is to be avoided. It is normal for bullets to have precisely the same nose shape and it is also normal for these same bullets to have nose lengths that can vary as much as .025″.
Summary of Cartridge Base To Ogive (CBTO) Discussion
Here are four important considerations regarding bullet seating depth as it relates to CBTO:
1. CBTO is a critical measurement to understand for handloaders because it’s directly related to precision potential, and you control it by simply setting bullet seating depth.
2. Tools and methods for measuring CBTO vary. Most of the measurement techniques have pitfalls (which may give rise to inconsistent results) that you should understand before starting out.
3. A CBTO that produces the best precision in your rifle may not produce the best precision in someone else’s rifle. Even if you have the same rifle, same bullets, same model of comparator gauges, etc. It’s possible that the gauges are not actually the same, and measurements from one don’t translate to the same dimension for another.
4. Once you find the CBTO that produces the best precision in your rifle, it’s important to allow minimal variation in that dimension when producing quality handloads. This is achieved by using quality bullets, tooling, and properly preparing case mouths and necks for consistent seating.
RELOADING TIP: Andris Silins has come up with a simple way to measure length to the lands in your rifle:
“Here’s what I did to find length to lands for seating my bullets. I made four cuts into the neck of fire-formed brass. Then I pressed the bullet in lightly and chambered the entire gauge. As the cartridge chambers, the bullet slides back into the case to give you length to lands. It took less than five minutes to get it cut and working. A little light oil in the barrel just past the chamber helps ensure the bullet does not get stuck in the lands. It works great and is very accurate.
I made the cuts using a Dremel with a cut-off wheel. You can adjust tension two ways. First, you can make the cuts longer or shorter. Longer cuts = less tension. If you used only three cuts insted of four you would get more tension. The trick is to be gentle when you open and close the bolt. If you ram the bolt closed you may wedge the bullet into the lands. When you open the bolt it helps to keep a finger or two near by to guide the case out straight because the ejector wants to push it sideways.”
Share the post "Make Your Own Length-to-Lands Gauge"
Now through April 30, 2009, MidwayUSA has the Hornady (formerly Stoney Point) Lock-N-Load Overall Length Gauge (item 570611) on sale for $25.99. That’s $4.50 off the regular price. Note, in addition to the Gauge itself, you’ll need a threaded modified case for each caliber you shoot, and we recommend having a comparator body with caliber-specific insert. The comparator allows you to measure from base of case to bullet ogive (rather than bullet tip).
OAL Gauge shown with Comparator to allow measurement from bullet ogive.
This Editor personally uses the Hornady Overall Length Gauge to find the distance to the lands for all his centerfire rifles. With practice, using the right technique, you can achieve measurements that are very repeatable. Here’s my method:
1. After screwing the modified case securely to the gauge, insert the case (with a bullet in neck) into the chamber. Make sure the modified (threaded) case goes ALL the way into the chamber. (Note: a heavily-fouled chamber can interfere with the seating of the modified case.)
2. Slide the gray pusher rod gently forward until you feel the first, slight resistance, then stop.
3. Now with the tip of your finger, tap the gray rod gently two or three times. This should give you a good, repeatable bullet contact with the lands, without going into the rifling.
4. You do NOT want to push hard on the gray rod. This will cause the bullet to engage the rifling. That will cause the bullet to stick, and you will end up with inconsistent length-to-lands measurements.
Some folks complain that this tool is not particularly repeatable. Well, if you use and practice the technique above, I think you’ll find the opposite is true. Using the Hornady OAL Gauge with a Berger bullet in a 6PPC, I recently measured length to lands five times in a row, with a couple witnesses to the procedure. Each of the measurements was consistent within .0007″ as recorded with a set of Mitutoyo Digital calipers. The key is using the same technique and pressure every time. CLICK HERE for a complete review of the Hornady OAL Gauge, with many photos
Share the post "Hornady (aka Stoney Point) OAL Gauge on Sale at MidwayUSA"
Effects Of Cartridge Over All Length (COAL) And Cartridge Base To Ogive (CBTO) – Part 1
